In portable electronic devices such as electronic notebooks, cellular phones, personal handyphone systems (PHS), digital cameras, music players, televisions, notebook personal computers, and game machines, adhesive tapes are used for fixing various members or modules, for example, for bonding a housing to a panel that protects an information display unit such as a liquid crystal display (LCD) or an organic electroluminescence display (OELD). Many of these portable electronic devices are provided with waterproofness. In such portable electronic devices, waterproofness is achieved by using an adhesive tape for fixing members.
For example, adhesive tapes that use a flexible foam as a base are disclosed as adhesive tapes having waterproof performance (refer to PTL 1 and PTL 2). It is disclosed that since these adhesive tapes have small thicknesses and good conformability, the adhesive tapes can be suitably used for providing portable electronic devices with waterproofness.
Regarding recent portable electronic devices such as smartphones, tablet personal computers, notebook personal computers, and game machines, the screen sizes of information display units of such portable electronic devices have been increasing. In addition, since the spaces occupied by such portable electronic devices tend to increase with the realization of higher functionality, a reduction in the thicknesses of adhesive tapes used in the portable electronic devices has been highly desired. There is also a high demand for adhesive tapes that have small widths and that can fix protective panels of information display units or information display device modules for the purpose of improving the degree of freedom of the design of the information display units. In the fixation of such information display units having large screen sizes or panels that protect the information display units using an ultra-thin adhesive tape and in the fixation of protective panels or information display device modules using an adhesive tape having a small width, the adhesive tape becomes easily separated when an impact due to falling or the like is applied. Thus, in addition to suitable conformability to an adherend, an improvement in impact resistance of adhesive tapes has been desired.
Furthermore, since components such as an image display module and a protective panel of portable electronic devices are expensive, there is also a high demand for reworkability. That is, it is also desirable that a fixed component be suitably separated in the case where a problem occurs in a portable electronic device during the fixation of the component or after the production of the device. However, adhesive tapes including foam bases, in particular, adhesive tapes having a small thickness and a small width tend to have low reworkability. Accordingly, an improvement in reworkability of adhesive tapes has also been desired.    PTL 1: Japanese Unexamined Patent Application Publication No. 2010-155969    PTL 2: Japanese Unexamined Patent Application Publication No. 2010-260880